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.TH INET_NTOP 3XNET "Nov 1, 2003"
.SH NAME
inet_ntop, inet_pton \- convert IPv4 and IPv6 addresses between binary and text
form
.SH SYNOPSIS
.LP
.nf
\fBcc\fR [ \fIflag\fR ... ] \fIfile\fR ... \fB-lxnet\fR [ \fIlibrary\fR ... ]
#include <arpa/inet.h>

\fBconst char *\fR\fBinet_ntop\fR(\fBint\fR \fIaf\fR, \fBconst void *restrict\fR \fIsrc\fR,
     \fBchar *restrict\fR \fIdst\fR, \fBsocklen_t\fR \fIsize\fR);
.fi

.LP
.nf
\fBint\fR \fBinet_pton\fR(\fBint\fR \fIaf\fR, \fBconst char *restrict\fR \fIsrc\fR, \fIdst\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBinet_ntop()\fR function converts a numeric address into a text string
suitable for presentation. The \fIaf\fR argument specifies the family of the
address. This can be \fBAF_INET\fR or \fBAF_INET6\fR. The \fIsrc\fR argument
points to a buffer holding an IPv4 address if the \fIaf\fR argument is
\fBAF_INET\fR,  or an IPv6 address if the \fIaf\fR argument is \fBAF_INET6\fR.
The \fIdst\fR argument points to a buffer where the function stores the
resulting text string; it cannot be \fINULL\fR. The \fIsize\fR argument
specifies the size of this buffer, which must be large enough to hold the text
string (\fBINET_ADDRSTRLEN\fR characters for IPv4, \fBINET6_ADDRSTRLEN\fR
characters for IPv6).
.sp
.LP
The \fBinet_pton()\fR function converts an address in its standard text
presentation form into its numeric binary form. The \fIaf\fR argument specifies
the family of the address. The \fBAF_INET\fR and \fBAF_INET6\fR address
families are supported. The \fIsrc\fR argument points to the string being
passed in. The \fIdst\fR argument points to a buffer into which the function
stores the numeric address; this must be large enough to hold the numeric
address (32 bits for \fBAF_INET\fR, 128 bits for \fBAF_INET6\fR).
.sp
.LP
If the \fIaf\fR argument of \fBinet_pton()\fR is \fBAF_INET\fR, the \fIsrc\fR
string is in the standard IPv4 dotted-decimal form:
.sp
.in +2
.nf
ddd.ddd.ddd.ddd
.fi
.in -2

.sp
.LP
where "\fBddd\fR"is a one to three digit decimal number between 0 and 255 (see
\fBinet_addr\fR(3XNET)). The \fBinet_pton()\fR function does not accept other
formats (such as the octal numbers, hexadecimal numbers, and fewer than four
numbers that \fBinet_addr()\fR accepts).
.sp
.LP
If the \fIaf\fR argument of \fBinet_pton()\fR is \fBAF_INET6\fR, the \fIsrc\fR
string is in one of the following standard IPv6 text forms:
.RS +4
.TP
1.
The preferred form is "\fBx:x:x:x:x:x:x:x\fR", where the '\fBx\fR's are the
hexadecimal values of the eight 16-bit pieces of the address. Leading zeros in
individual fields can be omitted, but there must be at least one numeral in
every field.
.RE
.RS +4
.TP
2.
A string of contiguous zero fields in the preferred form can be shown as
"\fB::\fR". The "\fB::\fR" can only appear once in an address. Unspecified
addresses ("\fB0:0:0:0:0:0:0:0\fR") can be represented simply as "\fB::\fR".
.RE
.RS +4
.TP
3.
A third form that is sometimes more convenient when dealing with a mixed
environment of IPv4 and IPv6 nodes is "\fBx:x:x:x:x:x:d.d.d.d\fR", where
the '\fBx\fR's are the hexadecimal values of the six high-order 16-bit pieces of
the address, and the '\fBd\fR's are the decimal values of the four low-order
8-bit pieces of the address (standard IPv4 representation).
.RE
.sp
.LP
A more extensive description of the standard representations of IPv6 addresses
can be found in RFC 2373.
.SH RETURN VALUES
.sp
.LP
The \fBinet_ntop()\fR function returns a pointer to the buffer containing the
text string if the conversion succeeds. Otherwise it returns \fINULL\fR  and
sets \fBerrno\fR to indicate the error.
.sp
.LP
The \fBinet_pton()\fR function returns 1 if the conversion succeeds, with the
address pointed to by \fIdst\fR in network byte order. It returns 0 if the
input is not a valid IPv4 dotted-decimal string or a valid IPv6 address string.
It returns \(mi1 and sets \fBerrno\fR to \fBEAFNOSUPPORT\fR if the \fIaf\fR
argument is unknown.
.SH ERRORS
.sp
.LP
The \fBinet_ntop()\fR and \fBinet_pton()\fR functions will fail if:
.sp
.ne 2
.na
\fB\fBEAFNOSUPPORT\fR\fR
.ad
.RS 16n
The \fIaf\fR argument is invalid.
.RE

.sp
.ne 2
.na
\fB\fBENOSPC\fR\fR
.ad
.RS 16n
The size of the \fBinet_ntop()\fR result buffer is inadequate.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
_
MT-Level	MT-Safe
.TE

.SH SEE ALSO
.sp
.LP
.BR inet_addr (3XNET),
.BR attributes (7)
